default_hostgroup: bump to 2.0.1 and include example config

```
Setting up ruby-foreman-default-hostgroup (9999-plugin+scratchbuild+201404291721) ...
root@wheezy335:~# ls /etc/foreman/plugins/
default_hostgroup.yaml.example
root@wheezy335:~# ls ~foreman/config/settings.plugins.d/
default_hostgroup.yaml.example
```

I'll merge to deb/develop as well